The invention generally relates to a mirror assembly having an electrically adjustable reflectivity, and more specifically to a mirror assembly that provides for the simultaneous display of a vehicle heading and an external temperature.
Mirror systems are known in the art that include a reflective element having a transmissive element of variable transmittance and a reflective surface disposed behind the transmissive element. Those mirror systems have used a drive signal coupled to the transmissive element of the mirror system so as to variably attenuate the reflectance of the mirror system. Typically, the transmissive element has included an electrochromic element. Examples of such mirror systems are disclosed in U.S. Pat. No. 4,902,108, entitled xe2x80x9cSINGLE-COMPARTMENT, SELF-ERASING, SOLUTION-PHASE ELECTROCHROMIC DEVICES SOLUTIONS FOR USE THEREIN, AND USES THEREOF,xe2x80x9d issued Feb. 20, 1990, to H. J. Byker; Canadian Patent No. 1,300,945, entitled xe2x80x9cAUTOMATIC REARVIEW MIRROR SYSTEM FOR AUTOMOTIVE VEHICLES,xe2x80x9d issued May 19, 1992, to J. H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled xe2x80x9cVARIABLE REFLECTANCE MOTOR VEHICLE MIRROR,xe2x80x9d issued Jul. 7, 1992, to H. J. Byker; U.S. Pat. No. 5,202,787, entitled xe2x80x9cELECTRO-OPTIC DEVICE,xe2x80x9d issued Apr. 13, 1993, to H. J. Byker et al.; U.S. Pat. No. 5,204,778, entitled xe2x80x9cCONTROL SYSTEM FOR AUTOMATIC REARVIEW MIRRORS,xe2x80x9d issued Apr. 20, 1993, to J. H. Bechtel; U.S. Pat. No. 5,278,693, entitled xe2x80x9cTINTED SOLUTION-PHASE ELECTROCHROMIC MIRRORS,xe2x80x9d issued Jan. 11, 1994, to D. A. Theiste et al.; U.S. Pat. No. 5,280,380, entitled xe2x80x9cUV-STABILIZED COMPOSITIONS AND METHODS,xe2x80x9d issued Jan. 18, 1994, to H. J. Byker; U.S. Pat. No. 5,282,077, entitled xe2x80x9cVARIABLE REFLECTANCE MIRROR,xe2x80x9d issued Jan. 25, 1994, to H. J. Byker; U.S. Pat. No. 5,294,376, entitled xe2x80x9cBIPYRIDINIUM SALT SOLUTIONS,xe2x80x9d issued Mar. 15, 1994, to H. J. Byker; U.S. Pat. No. 5,336,448, entitled xe2x80x9cELECTROCHROMIC DEVICES WITH BIPYRIDINIUM SALT SOLUTIONS,xe2x80x9d issued Aug. 9, 1994, to H. J. Byker; U.S. Pat. No. 5,434,407, entitled xe2x80x9cAUTOMATIC REARVIEW MIRROR INCORPORATING LIGHT PIPE,xe2x80x9d issued Jan. 18, 1995, to F. T. Bauer et al.; U.S. Pat. No. 5,448,397, entitled xe2x80x9cOUTSIDE AUTOMATIC REARVIEW MIRROR FOR AUTOMOTIVE VEHICLES,xe2x80x9d issued Sep. 5, 1995, to W. L. Tonar; and U.S. Pat. No. 5,451,822, entitled xe2x80x9cELECTRONIC CONTROL SYSTEM,xe2x80x9d issued Sep. 19, 1995, to J. H. Bechtel et al. Each of these patents is commonly assigned with the present invention and the disclosures of each, including the references contained therein, are hereby incorporated herein in their entirety by reference.
Optical display devices have also been provided behind the reflective element of such mirror systems in order to produce a single visual display of various information. Those optical display devices have typically been adapted to be viewed through the mirror system and have displayed various information which has included a vehicle direction, a time, or a temperature.
Various types of optical display devices have been utilized with mirror systems. For example, the optical display device could be an electroluminescent device, a vacuum fluorescent display, a light emitting diode (LED), semiconductor laser, incadescent, back-lit crystal display, cathode ray tube, or any number of other display technologies. In addition, multiple display devices have been implemented in the bezel of prior art rearview mirror assemblies.
While mirror systems have been disclosed in literature as having displays on which a wide variety of information is simultaneously displayed, such mirror systems have not been commercially practical due to their high levels of electromagnetic interference (EMI) or high cost. Auto manufacturers have imposed relatively strict limits on the EMI levels exhibited by interior rearview mirrors due to their close proximity to the radio antenna and other sensitive electronic equipment in the vehicle""s instrument panel. Currently, the EMI levels for a rearview mirror must typically be less than the limits in FIG. 7. Thus, mirror systems that have been commercially implemented have typically displayed only the vehicle heading or the external temperature at one time or use a non-multiplexed display which increases size and cost, so as to keep the EMI levels within acceptable limits.
An embodiment of the present invention is directed to a mirror assembly having an electrically adjustably reflectivity. The mirror assembly provides for the simultaneous display of a vehicle heading and an external temperature. The mirror assembly includes a reflective device, a dual display and a control circuit. The reflective device includes a transmissive element and a reflective surface formed on the transmissive element. The dual display is located behind the reflective surface of the reflective device. The dual display visually provides the vehicle heading and the external temperature through the reflective device. The control circuit provides for the variable attenuation of light through the transmissive element of the reflective device and controls the intensity and information displayed by the dual display. An advantage of the present invention is that it provides a dual display while exhibiting an electromagnetic interference level within acceptable limits. In addition, a single display driver is utilized to update the dual display such that the expense of using two display drivers is avoided.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.